Update Proton Calendar information (#2278)

Signed-off-by: Daniel Gray <[email protected]>

docs/calendar.md

@@ -39,7 +39,7 @@ Calendars contain some of your most sensitive data; use products that implement
 
     ![Proton](assets/img/calendar/proton-calendar.svg){ align=right }
 
-    **Proton Calendar** is an encrypted calendar service available to Proton members via web or mobile clients. Features include: automatic E2EE of all data, sharing features, import/export functionality, and [more](https://proton.me/support/proton-calendar-guide). Those on the free tier get access to a single calendar, whereas paid subscribers can create up to 20 calendars. Extended sharing functionality is also limited to paid subscribers.
+    **Proton Calendar** is an encrypted calendar service available to Proton members via web or mobile clients. Features include: automatic E2EE of all data, sharing features, import/export functionality, and [more](https://proton.me/support/proton-calendar-guide). Those on the free tier get access to 3 calendars, whereas paid subscribers can create up to 25 calendars. Extended sharing functionality is also limited to paid subscribers.
 
     [:octicons-home-16: Homepage](https://proton.me/calendar){ .md-button .md-button--primary }
     [:octicons-eye-16:](https://proton.me/legal/privacy){ .card-link title="Privacy Policy" }